This invention relates to a variable valve actuating apparatus for an internal combustion engine that is arranged to control an operating state of an intake valve or an exhaust valve in accordance with an engine operating condition, and a control shaft used for the variable valve actuating apparatus.
U.S. Pat. No. 5,988,125 (corresponding to Japanese Patent Application Publication No. 11-107725) shows a variable valve actuating apparatus including a drive shaft arranged to be rotated by a crank shaft; a drive cam integrally provided on an outer circumference of the drive shaft, a transmitting mechanism which is a multiple joint link, and which has a link arm, a link rod, and a rocker arm arranged to convert a rotational force of the drive cam to a swing motion; and a swing cam arranged to receive the motion of the drive cam. This swing cam is slid on an upper surface of a valve lifter, and arranged to open and close an intake valve and so on.
This rocker arm includes a first end portion rotatably connected through the link arm to the drive cam, and a second end portion rotatably connected through the link rod to the swing cam. This rocker arm includes a supporting hole formed at a substantially central portion in the longitudinal direction, and provided with an eccentric control cam integrally provided on a control shaft. The rocker arm is arranged to swing about the eccentric cam.
This variable valve actuating apparatus is arranged to control a rotational position of the control cam through the control shaft by an actuator in accordance with an engine operating condition, to vary a fulcrum (pivot point) of the rocker arm, and to vary a valve lift quantity and an operation angle of the intake valve by the swing cam.